A sweet sensor

Researchers at the University of Illinois at Urbana-Champaign have developed DNA sensors that can be used with
commercially available personal glucose meters to detect and quantify compounds other than
glucose.1 The researchers are now working to simplify the approach
and think the sensors could have use in diagnosing diseases or identifying environmental
contaminants.

"Despite tremendous efforts in developing
quantitative devices for sensing applications, few sensors are being used
widely by the public, with the notable exception of personal glucose meters,"
said Yi Lu, professor of chemistry at UIUC.

Personal glucose meters are small, portable devices that typically
cost less than $20. Because of their low price, ease of use and widespread
deployment, Lu and Yu Xiang, a postdoctoral researcher in the Department of
Chemistry at UIUC, decided the meters would be a good platform for detecting
and quantifying a variety of compounds beyond glucose in liquid samples.

The researchers repurposed the meter to indirectly
measure compounds of interest by implementing an intermediate step that would
translate the detected levels of a compound into a glucose readout.

To do this, the researchers designed a series of sensors
that consisted of magnetic beads attached to a complex of invertase and a DNA
enzyme or DNA aptamer that specifically interacts with the target molecule. In
the compound's presence, the DNA component releases invertase, a yeast-derived
enzyme that catalyzes the hydrolysis of sucrose into glucose, which in turn is
detected by the meter.

In proof-of-concept studies, the sensors enabled the
detection and quantification of cocaine, adenosine,
interferon-g
(IFNG;
IFN-g)
and uranium
with micromolar to nanomolar sensitivity.

The researchers used the Accu-Chek
Aviva blood glucose meter from the Roche
Diagnostics unit of Roche throughout the
study, which was published in Nature
Chemistry. For the cocaine sensors, the group also tested the Freestyle Lite and Ascensia Contour meters
from Abbott Laboratories and Bayer AG, respectively,
and found signal enhancement trends that were similar to those seen with the
Aviva meter.

Easy access

Now that they have
proof-of-concept data, the UIUC group plans to develop sensor
kits to generate samples that could be analyzed with commercial glucose meters.

Lu envisions three areas in which the technology could be
applied: in diabetic patients who want to measure additional markers in blood
to help better monitor their disease and aid doctors with treatment decisions;
for early detection of infectious diseases and cancer; and for indicating the
presence of environmental contaminants such as heavy metals, toxins and
pathogens.

He expects the shelf life of the DNA sensors will be about
six months and said the kits would be especially useful in resource-limited settings,
such as in remote areas with few medical facilities.

"Few existing quantitative assay systems could match
our method using glucose meters in terms of wide availability to the public,
portability, low cost and ease of use," Lu told SciBX. "While most existing assays
using laboratory-based instruments are efficient and sensitive, they are very
difficult for the public to use because of limited access to the instruments
and high cost."

His group is now trying to expand the range of compounds
that can be quantified with the approach and also is working to simplify the
process and make it more user friendly.

"Our current methodology does not require any
complicated device or operation, but it still has several steps including
sample addition, magnetic separation and liquid transfer," he said. "Our
ultimate goal is to develop an integrated design to make all the steps
automatic and have comparable simplicity to a typical personal glucose meter
test."

UIUC has filed patent applications covering the approach.
Lu said he is in licensing discussions with multiple parties.

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